Regarding DC plumbing, consider building a raised wood floor and run DC piping under that. I've seen that on a couple of websites and it looks like a very cool idea. What you lose by having a higher floor, you'd gain back by more clearance above, and you can run pipes under the floor to machines in the middle of the room without them being in the way as they would if dropped from the ceiling.
DC and electrical could go under the floor. Plus, that wood floor is going to have more give and be more comfortable over long shop sessions.
Of course, I speak from no experience with this (working in my 7' ceiling, concrete floor basement), but if I was building a shop from scratch, I'd probably want to work this idea in.
Good luck. And don't forget to leave bench space for cleaning skate bearings!